The invention relates to a process for preparing or purifying 4,4'-dihydroxy-alpha-substituted stilbenes.
The 4,4'-dihydroxy-alpha-substituted stilbenes prepared by the processes of the invention are useful in the preparation of liquid crystalline polycarbonates, polyestercarbonates, phenoxy thermoplastics, epoxy resins, polyarylates and polyesters. High purity 4,4'-dihydroxy-alpha-substituted stilbene can impart high performance properties in polycarbonates, polyestercarbonates, phenoxy thermoplastics, polyarylates and polyesters.
The reaction of alpha-haloketones with aromatic compounds, such as chloroacetone and 3-chlorobutanone with phenol and its ethers to yield 4,4'-dihydroxy-alpha-substituted stilbenes is known, see for example, J. Chem. Soc., pp. 3360-2 (1954). Typically, 4,4'-dihydroxy-alpha-methylstilbene is prepared via the condensation of chloroacetone and phenol in the presence of an acid. This process also yields substantial amounts of dimeric coproducts and other impurities; see, for example, U.S. Pat. No. 5,475,155. 4,4'-Dihydroxy-alpha-substituted stilbenes prepared by these processes are useful in thermoset polymer applications which do not require high purity. The impurities resulting from these processes make the 4,4'-dihydroxy-alpha-substituted stilbenes unacceptable for use in the production of thermoplastic polymers, such as polycarbonates, polyestercarbonates, phenoxy resins, polyarylates and polyesters. Also, the relatively substantial amounts of impurities produced by the process leads to a costlier process.
What is needed is a process for preparing or purifying 4,4'-dihydroxy-alpha-substituted stilbenes that can be performed efficiently with less cost and difficulty than current preparation or purification processes. What is also needed is a process that leads to a higher purity product than can be prepared under the current processes.